Tritrichomonas Infection in Cats: Symptoms, Testing and Treatment

By Dr Duncan Houston

Quick Answer

Tritrichomonas is a microscopic parasite that can cause recurring large-bowel diarrhoea, particularly in young cats living with other cats. Affected cats may still eat and play normally. Diagnosis needs an appropriate faecal test; symptoms alone cannot identify the cause. Prescription treatment requires careful veterinary supervision because the medicine used can cause serious adverse effects.

What is Tritrichomonas infection?

You may encounter both names, Tritrichomonas foetus and Tritrichomonas blagburni, in laboratory reports and older information. Current feline guidance uses T. blagburni for the feline organism. Infection spreads through faecal contamination, making shared litter facilities and crowded housing relevant risks. It is not considered a zoonotic infection, although routine hand hygiene remains sensible. See the ABCD trichomonosis guideline.

A positive result does not mean your home is dirty or that an affected cat cannot have a good quality of life. The useful questions are whether infection explains this cat's signs, what other problems need investigation and which management plan offers the best balance of benefit and risk.

Symptoms and when to get help

What you notice	Possible significance	Next action
Frequent soft stools, mucus, fresh red blood or straining	Large-bowel inflammation, with several possible causes	Arrange a veterinary examination and discuss faecal testing
Diarrhoea in several cats	A shared infectious or dietary problem may be present	Tell the vet about every affected cat and their shared resources
Weakness, repeated vomiting, poor intake or dehydration	More serious illness or complications	Seek urgent veterinary advice, especially for a kitten
Wobbliness, tremors, unusual behaviour or seizures during treatment	Possible medicine toxicity	Give no further dose and contact an emergency vet immediately
Repeated tray visits with little or no urine	A urinary blockage can resemble bowel straining	Emergency veterinary assessment

How the vet establishes the cause

Giardia, intestinal worms, food-related problems and chronic inflammatory disease can produce overlapping signs. Some cats have more than one condition. Bring a stool diary, photographs and a list of previous medicines, diets and test results rather than assuming every recurrence is the same infection.

PCR testing is commonly used to look for the organism's genetic material. Sample collection and recent treatment can affect interpretation, so ask the clinic exactly how to collect and store a sample. A routine worm test is not automatically a Tritrichomonas test. Your vet may recommend further sampling if suspicion remains despite a negative result.

Treatment needs an individual decision

Ronidazole is the medicine with established evidence of effectiveness, but it has a narrow safety margin and does not reliably cure every infection. It is not a routine, licensed feline wormer. Compounded preparations and handling instructions need particular care. Never use a dose found online or another animal's prescription. North Carolina State University's diagnostic laboratory explains these treatment limitations and the lack of a straightforward alternative.

Ask the prescribing vet what benefit they expect, how to handle the medication safely, which signs require stopping it and how follow-up will work. Tell them if your cat is pregnant, nursing, very young or taking other medicines. Improving stools alone does not prove the organism has been eliminated; infection may persist after diarrhoea settles.

A practical plan for the household

Agree on testing first. Identify which cats need samples rather than automatically medicating everyone.
Keep a daily record. Track stool consistency, appetite, weight where practical and medication times.
Remove faeces promptly. Clean trays and soiled surfaces, wash hands and keep food preparation areas separate from litter equipment.
Reduce contamination. Ask about separate trays and cleaning equipment for affected cats; avoid stressful isolation without a workable welfare plan.
Keep feeding consistent. Use the diet your vet recommends and avoid repeated food changes while assessing progress.
Attend follow-up. Review persistent signs and testing needs before extending or repeating treatment.

Common mistakes to avoid

Repeated courses of leftover antibiotics, home-made drug doses and harsh cleaning chemicals can add harm without resolving the infection. Do not mix disinfectants. Follow product directions and keep cats away until surfaces are appropriately rinsed or dry. A temporarily normal stool is not a reason to change a prescribed course without advice.

Frequently asked questions

Can an infected cat look healthy?

Yes. Some cats remain bright despite diarrhoea, and others carry infection without obvious signs. Appearance alone cannot replace testing.

Will ordinary worming solve it?

No. Tritrichomonas is not a worm, and standard worming products do not reliably treat it.

Should I treat every cat in the house?

Not automatically. Discuss testing, symptoms and the risks of treatment with your vet before deciding.

Can it come back?

Persistent infection, reinfection or a different bowel problem can all explain returning diarrhoea. Reassessment is safer than automatically restarting medicine.

The next useful step

For a cat with recurring diarrhoea, arrange an examination and a clear sampling plan. Consistent records and careful follow-up are more useful than cycling through unproven treatments.

For more practical cat-health education, visit ASK A VET™. Persistent diarrhoea and suspected medicine reactions need advice from your own veterinary team.